Backgroundworks blog is about the mechanisms in the background of various things around us. I hope it helps to get a deeper understanding of things.
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Most of us love riding on bikes and some of us prefer to ride on a gearless bike due to various reasons. Many of us are aware about how transmission in a bike works but only few of us know how power is transmitted in a gearless vehicle and if you are interested to learn that, this is what that happens in the back ground.
When we talk about transmission in vehicles the first thing that strikes our mind is gears. In gearless bikes as the name itself suggests there are no gears in transmission. The gearless vehicle transmission involves CVT.
CVT stands for Continuously Variable Transmission. In this type of transmission we have infinite number of gear ratios between the maximum and minimum values. The maximum and minimum values are determined maximum and minimum pulley diameters which shall be discussed in below.
A CVT consists of following parts:
Primary pulley
Secondary pulley
Belt
Here the word pulley literally doesn't mean a pulley. Each pulley consists of two sheaves one of which is stationary and the other moves far and close to stationary sheave which eventually changes the diameter of pulley on which the belt rotates. The sheaves are conical in shape.
The Primary pulley is also called Driver pulley which is connected to the crankshaft of the engine, the moving sheave in driver pulley is called variator. The Secondary pulley is also called Driven pulley is connected to output shaft. The belt is generally made of steel. Generally centrifugal clutches are used in CVT.
When ever we start our gearless bike engine the crankshaft rotates. At idle speed the clutch is not engaged and the vehicle is stationary, This is like a neutral position in case of bikes with gear transmission. When we rise the acceleration throttle as the clutch engages the vehicle will be in motion.
Once the vehicle is moving and when we want to increase the speed we rise the throttle high as a result the crankshaft rotates even faster and the variator connected to it also rotates at high rpm. The variator consists of weights in it, whenever speed increases the weights move outward due to centrifugal force. As a result of this the variator move closer to stationary sheave thus increasing the pulley diameter.
Because the belt length is fixed, When the diameter of driver pulley increases more length of belt is around it and as a result belt is pulled down to center of driven pulley and the movable sheave moves away from stationary sheave. But when we reduce the speed the movable sheave should return to it's position. This action is taken care by the contra spring present between clutch and movable sheave.
Most of us have heard about 3-D Printing in many situations of our life. We know that a 3-D Printer produces a 3-D object, but how many of us know what exactly happens in the background? If you are keen to know check this out.
As a part of learning let us know what exactly is 3-D printing and when it was evolved before going into the working of it.
3-D printing is previously referred to as Additive Manufacturing(AM). AM is the means of creating an object by adding material to the object layer by layer. AM has various names like Stereolithography, 3-D Layering and 3-D printing. AM was used for rapid prototyping in manufacturing industries to create prototypes of the actual product.
3-D Printing came into existence in early 1980's. In 1981, Hideo Kodama of Nagoya Municipal Industrial Research Institute invented two AM fabricating methods of a three-dimensional plastic model with photo-hardening polymer, where the UV exposure area is controlled by a mask pattern or the scanning fiber transmitter. Then in 1984, Chuck Hull of 3D Systems Corporation, developed a prototype system based on this process known as stereolithography, in which layers are added by curing photopolymers with ultraviolet light lasers. Hull's contribution is the design of STL file format widely accepted by 3-D printing software as well as the digital slicing and infill strategies common to many processes today.
Let us know what kind of processes are there in 3-D Printing.
1) Direct 3-D Printing
In Direct 3-D printing we have thick waxes and plastic polymers which are extruded (dispensed) from the nozzle to print the object. These printers use inkjet technology. The nozzle can move back and forth to make a layer, it moves up and down to make layer over layer. Once a layer is made the wax or polymer solidfy to form a firm cross-section of the object. Rapid prototyping has been major factor for growth of direct 3-D printing. Rapid prototyping products use technologies such as multi-jet modeling (MJM), which creates wax prototypes quickly with dozens of nozzles
2) Binder 3-D Printing
The Binder printing uses two separate materials that come together to form each printed layer: a fine dry powder plus a liquid glue, or binder. Binder 3-D printers make two passes to form each layer. The first pass rolls out a thin coating of the powder, and the second pass uses the nozzles to apply the binder. The building platform then lowers slightly to accommodate a new layer of powder, and the entire process repeats until the model is finished. This method can incorporate a wider variety of materials in the process, including metals and ceramics, as well as color.
3) Photopolymerization
Photopolymerization is a 3-D printing technology whereby drops of a liquid plastic are exposed to a laser beam of ultraviolet light. During this exposure, the light converts the liquid into a solid. Stereolithography Apparatus(SLA) uses photopolymerization, directing a laser across a vat of liquid plastic called photopolymer. As with inkjet 3-D printing, the SLA repeats this process layer by layer until the print is finished.
4) Selective Laser Sintering
Selective Laser Sintering is an Additive manufacturing process that builds three dimensional parts by using a laser to selectively sinter (heat and fuse) a powdered material, which then solidifies to form the printed layer.
No matter which approach a 3-D printer uses, the overall printing process is generally the same. In their book "Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing," Ian Gibson, David W. Rosen and Brent Stucker list the following eight steps in the generic AM process:
Step 1: CAD -- Produce a 3-D model using computer-aided design (CAD) software. The software may provide some hint as to the structural integrity you can expect in the finished product, too, using scientific data about certain materials to create virtual simulations of how the object will behave under certain conditions.
Step 2: Conversion to STL -- Convert the CAD drawing to the STL format. STL, which is an acronym for standard tessellation language, is a file format developed for 3D Systems in 1987 for use by its stereolithography apparatus (SLA) machines. Most 3-D printers can use STL files in addition to some proprietary file types such as ZPR by Z Corporation and ObjDF by Objet Geometries.
Step 3: Transfer to AM Machine and STL File Manipulation -- A user copies the STL file to the computer that controls the 3-D printer. There, the user can designate the size and orientation for printing. This is similar to the way you would set up a 2-D printout to print 2-sided or in landscape versus portrait orientation.
Step 4: Machine Setup -- Each machine has its own requirements for how to prepare for a new print job. This includes refilling the polymers, binders and other consumables the printer will use. It also covers adding a tray to serve as a foundation or adding the material to build temporary water-soluble supports.
Step 5: Build -- Let the machine do its thing; the build process is mostly automatic. Each layer is usually about 0.1 mm thick, though it can be much thinner or thicker. Depending on the object's size, the machine and the materials used, this process could take hours or even days to complete. Be sure to check on the machine periodically to make sure there are no errors.
Step 6: Removal -- Remove the printed object (or multiple objects in some cases) from the machine. Be sure to take any safety precautions to avoid injury such as wearing gloves to protect yourself from hot surfaces or toxic chemicals.
Step 7: Postprocessing -- Many 3-D printers will require some amount of post-processing for the printed object. This could include brushing off any remaining powder or bathing the printed object to remove water-soluble supports. The new print may be weak during this step since some materials require time to cure, so caution might be necessary to ensure that it doesn't break or fall apart.
Step 8: Application -- Make use of the newly printed object or objects.
The following video illustrates various applications
Most of us watch bullets being fired from the guns in many action movies. Ofcourse for us, buying a gun is subjected to the country's federal laws. Whether you own one or not, if you have ever wondered how bullet gets it speed when gun is fired, Then this is what that happens in the background.
There are many sizes of guns right from the smallest Miniature Revolver C1ST to the largest Schwerer Gustav( Railway gun). They all have bullets of corresponding sizes. Let us know in brief how bullets evolved before knowing how bullet gets it's speed.
"Bullet" is derived from the French word boulette which roughly means little ball. Originally, bullets were made out of stone or purpose-made clay balls used as sling ammunition, as weapons and for hunting. Eventually as firearms were developed, these same items were placed in front of a propellant charge of gunpowder at the end of a closed tube. As firearms became more technologically advanced, from 1500 to 1800, bullets changed very little. They remained simple round (spherical)lead balls, called rounds, differing only in their diameter.
The original musket bullet was a spherical lead ball smaller than the bore, wrapped in a loosely fitted paper patch which served to hold the bullet in the barrel firmly upon the powder. Bullets that were not firmly upon the powder, when fired caused the barrel to explode, with the condition known as a short start.
Later Square bullets, invented by James Puckle and Kyle Tunis, were briefly used in one version of the Puckle gun. The use of these was soon discontinued due to irregular and unpredictable flight patterns.
Later the pointed bullets are developed and were resisted to be used at the beginning for various reasons and were later accepted. The next important change in the history of the rifle bullet occurred with invention of the copper-jacketed bullet, which is an elongated bullet with a lead core in a copper jacket.
The surface of lead bullets fired at high velocity may melt due to hot gases behind and friction with the bore. Because copper has a higher melting point, and greater specific heat capacity and hardness, copper-jacketed bullets allow greater muzzle velocities.
Bullet designs have to solve two primary problems. In the barrel, they must first form a seal with the gun's bore.The bullet must also engage the rifling without damaging or excessively fouling the gun's bore, and without distorting the bullet. These interactions between bullet and bore are termed internal ballistics. Bullets must be produced to a high standard, as surface imperfections can affect firing accuracy.
A bullet generally consist of 5 main parts. They are:
Bullet
Casing
Propellant
Rim
Primer
The bullet is what that actually hits the target. Propellant is the explosive that gives necessary force to the bullet to hit the target, it occupies about two thirds of a typical bullet's volume. Casing holds all parts together. Primer is like a fuse which ignites the propellant and rim provides the extractor on the firearm a place to grip the casing to remove it from the chamber once fired.
When the trigger is pulled a spring mechanism hammers a metal firing pin into the back end of the bullet, igniting the small explosive charge in the primer. The primer then ignites the propellant, as the propellant chemicals burn, they generate lots of gas very quickly. The gas shoots from the back of the bullet, increasing the pressure behind it, and forcing it down the gun barrel at extremely high speed of around 300 m/s. The speed of bullet depends on various factors. here is video to help you understand better.
The primer is a metal cup containing a primary explosive inserted into a recess in the center of the base of the cartridge. A primary explosive is an explosive that is extremely sensitive to stimuli such as impact, friction, heat, static electricity, or electromagnetic radiation. A relatively small amount of energy is required for initiation. As a very general rule, primary explosives are considered to be those compounds that are more sensitive than PETN. Upon being struck with sufficient force, a primer reacts chemically to produce heat which ignites the main propellant charge and fires the projectile (bullet).
The propellant chemicals in a handgun bullet are not designed to explode suddenly all at once, that would blow the whole gun open and very likely kill the person firing it. Instead, they are supposed to start burning relatively slowly, so the bullet moves off smoothly down the gun. They burn faster as the bullet accelerates down the barrel, giving it a maximum "kicking" force just as it comes out of the end. As the bullet emerges, the whole gun recoils because of a basic law of physics called "action and reaction" or Newton's third law of motion. When the gas from the explosion shoots the bullet forwards with force, the whole gun jolts backwards with an equal force in the opposite direction. The propellant used could be either gunpowder or cordite.
Previously revolvers used to be the hand guns, now we have semi automatic pistols. The two videos show the animation of how they work.
The recent advancements in technology developed guns with target locking options. More recent developments led to smart bullets which follow the target and takes it down. This saves the rounds and comes handy when the target is surrounded.
Notify me about anything you want to know in the comments. Thanks and peace.
Most of us own cars these days. We often open and close the windows on our cars for various purposes. Do you know what happens in the background to open and close the window? Here is the description about what happens in the background
Before going to know about window mechanism, lets know how glass entered into automobile.
When automobile was invented, It didn't had a closed body. The drivers had nothing to protect them from the dust, bugs and a face full of mud while driving the car. So, this is when a windshield came into existence. It was around the early 1900's when the windshield was introduced.
The first windshields were two-piece affairs, when mud, rain, or other substances blocked his or her view forward, a driver could simply tip the top half down for an unobstructed view. While the usefulness of windshields was clear to everybody, they posed a serious danger. Manufacturers quickly discovered that during an accident, their glass windshields could shatter, sending a shower of sharp shards into the vehicle. Glass windshields proved most hazardous during front-end collisions, when passengers could end up smashing headlong through the glass.
Here is a picture to help you understand
Later changes
when the first cars with glass on all four sides were introduced, many people were afraid to ride in them. In early 20th century, two European scientists independently invented a solution to deadly windshields. While working in his lab, French scientist Edouard Benedictus accidentally knocked a flask to the floor. To his amazement, the glass did not break. Looking closer, he discovered that the chemical that had been inside the flask, nitrocellulose, had dried up, leaving an adhesive film that kept the numerous bits of fragmented glass from separating. Benedictus went on to develop a window consisting of two layers of plate glass held together by layer of cellulose. After windshield was developed, there were cars with no windows on sides. Like the one below.
Later the car had windows on all sides.Different window styles were opted by various manufacturers for their car models. Some used fixed windows, some used horizontal sliding windows, Opera windows.
Finally in 1948 the crank windows were introduced. These are outdated now as most of the cars are coming with power windows, although low end models of some cars are still using this feature.
The first thing that lies beneath your car window is a window regulator.The window regulator is the component inside your door panel that allows you to raise or lower your window glass. Both manual and electric car windows have window regulators. A manual window is operated by a hand-crank, while an electric window is controlled by a switch or button that activates a motor.
A manual window regulator is the most basic of window lifting mechanisms. It has crank handle sticking through the door panel that regulates the up and down motion of the glass window. Humans power this type of regulator by their wrist, as the window crank needs to be physically rotated to raise and lower the door glass.
When we rotate the crank, we actually rotate a pinion which is engaged to a larger gear, which is inturn connected to the window regulator that moves your window up and down. It converts rotary motion to linear motion.
In power windows we have a motor to which we supply power from battery. When we press the power button to lift window we actually make circuit and current flows to motor. The motor is attached to a worm gear and several other spur gearsto create a large gear reduction and provides enough torque to lift the window.
In power windows we have three kinds of mechanisms. They are:
1. The Scissors Mechanism The scissor type window regulator basically look like a giant pair of scissors. As they expand, the window goes up. When they contract, the window glass rolls down. The drawback of this type of regulator is that the wheels on the ends of them wear out over time, and break off. This causes your door glass to tilt sideways, and eventually fall down into the door. They also wear out at the center of the scissor mechanism and become noisy, sloppy, and unpredictable.
2. The Cable Mechanism
The cable type window regulator is a more modern design that is used in a huge variety of vehicles. They use far less space inside the door. Being more complicated than the scissor-type, these window regulators have more opportunity to break. The pulleys and cables in these regulators typically wear out, and snap. When that happens, the glass almost always falls inside the door, leaving your interior open.
3. The Flexible Drive Mechanism
This window mechanism was used for the rear doors in Reliant and Sundance 4-door models. The mechanism was a rack-and-pinion gear set made of tough injection-molded Delrin plastic. The Delrin rack gear was flexible and slides along a T-shaped steel track to move the glass up or down as the window crank turns the pinion gear. The window glass was fastened to the sliding rack gear by a link. A small fixed window was used in the door behind the sliding glass with this mechanism.
This video will help you to know about the electrical circuits in power windows.
Have you ever wondered how your car starts just by turning a key or pushing a start button? If you ever did, here is what that happens in the back ground.
First let us know what is essential for engine to start and run. Fuel and spark are main requirements for the engine to keep running, but to start an engine initially we need to rotate crankshaft which in turn reciprocates the pistons in cylinder block. This is done by the Flywheel attached to crankshaft. The flywheel has teeth which engages with pinion teeth on starter.
To start car engine we rotate the ignition key beyond the ON symbol. After a few jerky sounds you hear your engine breathing. When we rotate the ignition key beyond the ON indication the starter switch turns ON and the current from the car battery is drawn to the solenoid through thick wires. When current passes through solenoid wires electromagnetic field develops and attracts the iron rod inside it. The movement of iron rod completes the circuit between battery and the starter. Now the starter motor powers the pinion on the motor shaft.
Bendix drive is engagement mechanism used in starter motors. The device allows the pinion gear of the starter motor to engage or disengage the flywheel of the engine automatically when the starter is powered.It disengages as soon as the engine picks up speed, and there are two ways by which it does so - the inertia system and the pre-engaged system.
Inertia System
Pre Engaged System
When the starter motor begins turning, the inertia of the drive pinion assembly causes it to wind the spring forcing the length of the spring to change and engage with the ring gear. When the engine starts, backdrive from the ring gear causes the drive pinion to exceed the rotative speed of the starter, at which point the drive pinion is forced back and out of mesh with the ring gear.The pinion returns so violently that there has to be a strong spring on the shaft to cushion its impact.The violent engagement and disengagement of an inertia starter can cause heavy wear on the gear teeth.
To overcome that problem the pre-engaged starter was introduced, which has a solenoid mounted on the motor. As well as switching on the motor, the solenoid also slides the pinion along the shaft to engage it.The shaft has straight splines rather than a Bendix thread, so that the pinion always turns with it.The pinion is brought into contact with the toothed ring on the flywheel by a sliding fork. The fork is moved by a solenoid, which has two sets of contacts that close one after the other.The first contact supplies a low current to the motor so that it turns slowly - just far enough to let the pinion teeth engage. Then the second contacts close, feeding the motor a high current to turn the engine.The starter motor is saved from over-speeding when the engine starts by means of a freewheel clutch, like the freewheel of a bicycle. The return spring of the solenoid withdraws the pinion from engagement.
The ignition switch(Key rotating port) has a return spring, so that as soon as you release the key it springs back and turns the starter switch off.
In olden days the driver used to rotate the flywheel manually to start the engine (Cranking). See 11.52 min in the video below.
Want to know more about starter go to following links:
So, We have successfully started the car and as stated above fuel and spark are required. Fuel, we would fill it the car at gas station. So where does the spark come from.To generate the spark we need high voltage. But the car battery can only provide 12V. We need to convert this 12V from battery to thousands of volts. Lets learn about spark generation.
When we turn on the ignition switch to ON position, current flows from 12 volt car battery to the ignition coil. An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system which transforms the battery's low voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel. Ignition coil consists of laminated iron core surrounded by Primary and secondary windings.
The current flows from the battery to the primary winding in the Ignition coil and flows to a mechanical contact breaker which is grounded at other end. The contact will be broken by a cam which is connected directly to the cam shaft according to the number of engine cylinders. When the contact is broken, the current flow in primary circuit breaks and an EMF is induced in the secondary winding which has more no. of coil turns than primary winding. The voltage jumps to a value of some thousands. Whenever the contact is broken back EMF generated is absorbed by the condenser.
The generated high voltage is then carried to distributor by spark plug wires also known as high tension leads. In the distributor we have a rotor that rotates according to ignition timing, such that it supplies current to a exact spark plug at exact time through distributor points. The rotor does not come directly into contact with the distributor point.
The high voltage is then transferred to the spark plug central electrode by high tension leads. The central electrode is surrounded by an insulator. The central electrode and ground electrode are separated by very small distance. When the voltage exceeds the dielectric strength of gases between the electrodes, the gas is ionised and spark is produced with current flow in the gap. Originally, every ignition coil system required mechanical contact breaker points, and a capacitor (condenser).
The following video helps in better understanding.
More recent electronic ignition systems use a power transistor to provide pulses to the ignition coil. In this system the mechanical contact breaker is replaced by an armature and electronic ignition module( EIG). Previously contact breaker used to break current in primary circuit and the mechanical system is always prone to wear. In this system the armature sends signal to ignition module to make and break the circuit. This setup has armature which has teeth and a pickup coil. When the armature tooth comes in front of pickup coil it sends a signal to EIG to break current flow in primary circuit. When the tooth moves away the primary circuit is made. Rest of the mechanism is the same.
The following video helps in better understanding.
We have another Ignition system which is the Direct Ignition System (DIS). In this system the distributor is eliminated and we have Ignition Control Module (ICM) and Engine Control Unit (ECU). We have sensors to know the exact position of cam shaft and crank shaft. The signals from both the sensors help ICM determine the position of piston w.r.t the position of crank shaft and cam shaft. These sensors also help ICM in advancing or retarding the spark with varying engine speeds. This is possible as each spark plug is individually powered by the coil pack (ignition coils) i.e one coil pack per plug.The ECU supplies battery voltage to coil pack and simultaneously calculates the ignition timing, which is based on information it gets from ICM.
We can also have common coil pack between two spark plugs and the cylinder block acts as the connection between the two plugs. In this type of DIS one plug fires in forward direction whereas the other spark plug in companion cylinder fires in opposite direction. This system results in waste spark generation. The wasted spark system is more reliable than a single coil system with a distributor and less expensive than coil-on-plug.
The following video helps in better understanding.
Diesel engines doesn't need spark plugs. Diesel engines rely on fuel compression for ignition, but usually also have glowplugs that preheat the combustion chamber to allow starting of the engine in cold weather.
Some topics you would want to learn more in detail :
